Asthma is associated with endometriosis: A retrospective population-based cohort study

Background: Evidence regarding the association between asthma and endometriosis is limited and inconsistent. The goal of the study was to investigate whether women diagnosed as having asthma were at a greater risk of endometriosis than age-matched unaffected women. Methods: We conducted a nationwide population-based retrospective study by using data retrieved from the Taiwan National Health Insurance Research Database during the period of 2000-2005 with follow-up through 2013. The current analysis included 7337 women aged 12-50 years with newly diagnosed asthma and using asthma-related medications and 29,348 age-matched women without asthma. A Cox proportional hazards regression model was used to estimate the risks of endometriosis in women with asthma as compared with those without asthma. Results: The overall risk of endometriosis in the asthma group was 1.50-fold higher (95% confidence interval = 1.33-1.70) than that in the nonasthma group. A stratified analysis by age further revealed that patients with asthma were associated with a higher risk of endometriosis in age groups of 21-50 years. Conclusion: Compared with women without asthma, women with asthma of reproductive age are at a higher risk of endometriosis. Additional studies are warranted to elucidate the mechanism(s) underlying the association between asthma and a higher risk of endometriosis.